This invention relates to an internal combustion engine ignition device having a control unit including a control circuit which is covered with resin by molding and held in a casing in which an ignition coil is set.
FIG. 6 is a broken view showing a conventional internal combustion engine ignition device. In FIG. 6, reference numeral 6 designates an IC package including a power switch made up of a current limit circuit or the like which is covered with resin; 7, a heat sink for effectively radiating heat from the IC package; and 9, a holder holding the IC package 6.
Further in FIG. 6, reference numeral 10 denotes a casing including an accommodating section 11 for accommodating the ignition coil (not shown) and the IC package 6, and a connector section 12; and 13, a guide used to accommodate the IC package 6 in the accommodating section 11.
The conventional internal combustion engine ignition device suffers from the following difficulty: In general, the internal combustion engine ignition device is used in a severe environment in which the temperature changes from high to low, and vice versa, repeatedly. In this case, a thermal stress is set up by the difference in the coefficient of linear expansion between the assembly of the IC package 6 and the heat sink 7, and the casing 10. Therefore, the casing 10 may be cracked by the shearing stress between these parts.
Accordingly, an object of the present invention is to eliminate the above-described difficulty accompanying a conventional internal combustion engine ignition device. More specifically, an object of the present invention is to provide an internal combustion engine ignition device which is high in durability under severe environmental conditions.
A further object of the invention is to provide an internal combustion engine ignition device which is high in assembling efficiency.